Most people know the 1st Bitcoin TX from Satoshi to Hal, in block 170.

But did you know the 2nd TXs we know Satoshi made to someone was to

Dustin Trammell in block 524 for 25 BTC.

Cryptographically proven by Dustin.

However between the TX in Block 170 to Hal until the one shown above, we can see there were 7 other transactions made.

Looking at how the funds flowed, it seems Satoshi was making test payments to hiself.